The following procedure shows you how to create a range of hills and mountains.

To modify terrain height

In the Rollup Bar, click the Terrain tab
and then click Modify.

Under Modify Terrain, click Rise/Lower
and use the following settings to create gentle hills in your scene:

Outside Radius = 25

Inside Radius = 1

Hardness = 0.25

Height = 3

In the Perspective viewport, navigate towards the outer
perimeter of the terrain map and click or drag to paint on the terrain. Experiment
with clicking and dragging along the terrain to manipulate the terrain to different
heights. Build some larger hills of different sizes and shapes.

Modify the brush settings to the following:

Inside Radius = 20

Hardness = 1

Height = 1

Paint again on the terrain. Notice how the terrain rises up straight and
rigid.

Click the Smooth tool and use the following settings:

Outside Radius = 25

Hardness = 0.2

Paint with the smooth brush over the last area of terrain you created. Notice the
smoothing of the terrain.

Click Pick Height and click on a high point on the terrain.
Notice that the Height setting in the tool adjusts to the
height you clicked on.

Select a point on the terrain where the height was unchanged. The
Height setting in the Modify Terrain
tool changes to 32 (the default terrain height). This tool does not affect your
terrain directly but simply adjusts settings for the next step.

Click Flatten, and use the following settings:

Outside Radius = 25

Inside Radius = 0

Hardness = 1

Paint with the Flatten tool over the area you just smoothed.
The terrain flattens to the same height as the rest of the default terrain
height.

Using the terrain height tools, create a range of high and long hills that vary to
create visual interest.

Use the Smooth tool to soften where you like.
With time and experimentation, you can make your terrain look like the following
picture.